Chapter 6: Resistance Exercise for Impaired Muscle Performance

Introduction

Muscle performance is the capacity of a muscle to do work (force × distance).⁹ Despite the simplicity of the definition, muscle performance is a complex component of functional movement and is influenced by all of the body systems. Factors that affect muscle performance include the morphological qualities of muscle; neurological, biochemical, and biomechanical influences; and metabolic, cardiovascular, respiratory, cognitive, and emotional function. A healthy and fully functioning muscular system is critical for not only meeting the physical demands imposed on the body, but for allowing individuals to be mobile, recreate, work, and pursue meaningful experiences.

The key elements of muscle performance are strength, power, and endurance.⁹ If any one or more of these elements is impaired, activity limitations and participation restriction or increased risk of dysfunction may ensue. Factors such as injury, disease, immobilization, disuse, and inactivity may impair muscle performance, leading to weakness and muscle atrophy. When deficits in muscle performance are present, resistance exercises are an appropriate therapeutic intervention to select.

Resistance exercise is an activity in which dynamic or static muscle contraction is resisted by an outside force applied manually or mechanically.^95,236 Resistance exercise, also referred to as resistance training,^6,7,161 is an essential element of rehabilitation programs for persons with impaired function. In addition, resistance exercise is an integral component of conditioning programs for those who wish to promote or maintain health and physical well-being, enhance performance of motor skills, and reduce the risk of injury and disease.^6,7,231

A comprehensive examination and evaluation of the patient or client are the foundations on which a therapist determines whether a program of resistance exercise is warranted and likely to be effective. Many factors will influence this determination and decisions about how the exercises are designed, implemented, and progressed. Factors such as the underlying pathology; the extent and severity of muscle performance impairments; the presence of other deficits; the stage of tissue healing after injury or surgery; and the patient's or client's age, overall level of fitness, and ability to cooperate and learn must all be considered. Once a resistance exercise program is developed and prescribed, the therapist should initially implement the program directly or teach and supervise the exercises to ensure a smooth transition to an independent, home-based program.

This chapter provides a foundation of information on resistance exercise, identifies the determinants of resistance training programs, summarizes the principles and guidelines for application of manual and mechanical resistance exercise, and explores a variety of regimens for resistance training. It also addresses the available scientific evidence on the relationship between improvements in muscle performance and enhanced functional abilities. The specific techniques described and illustrated in this chapter focus on manual resistance exercise for the extremities, primarily used during the early phase of rehabilitation. Additional exercises performed independently by the patient ...